Foam structural element



Oct. 14, 1969 R. A. HITCH FOAM STRUCTURAL ELEMENT Filed June 9, 1964INVENTOR. d )y' BY 2%!!! my, ii/Y5K;

United States Patent 3,472,728 FOAM STRUCTURAL ELEMENT Robert A. Hitch,Cincinnati, Ohio, assignor to Pullman Incorporated, Chicago, Ill., acorporation of Delaware Filed June 9, 1964, Ser. No. 373,694 Int. Cl.B3215 3/12, 5/18, 7/00 US. Cl. 161-69 4 Claims ABSTRACT OF THEDISCLOSURE This invention relates to an insulated panel and moreparticularly the invention is directed to a pre-fabricated sandwich of aplastic foamed between a pair of spaced parallel sheets. Still morespecifically, the invention is directed to an insulated panel which isused primarily in the floor of a refrigerated cargo body or otherenvironment in which it is subjected to compressive loading.

In the past, it has been the practice to construct such panels of a pairof spaced plywood sheets having elongated two by fours spacing thesheets apart with the plastic material foamed-in-place between thesheets. In the co-pending application of George R. Hefiner, Ser. No.371,426, filed June 1, 1964, it has been pointed out that there are manyadvantages to be derived from the elimination of the wood cross bolstersand the substitution therefor of a material which is substantiallyentirely the foam employed to fill the major portion of the spacebetween the two sheets. The substitution of the foam for the woodspacers results in a structure which has superior insulative qualitiesand which is markedly lighter in weight, thereby increasing the pay-loadwhich can be carried by the cargo container.

The difficulty with the substitution of a plastic foam for the wood insuch floor panels is that that plastic foam does not even approach theability of wood to withstand compressive loading. In addition to itsinsulative qualities, the floor panel of the type to which the presentinvention is directed must Withstand compression stress and musttransmit the compression load on its upper surface to the transversevehicle frame members which support the floor panels.

Heffner, in the co-pending application, has disclosed the combination ofa tubular paper or plastic skin and foam united to form discs whichexhibit a remarkable compression strength. He has also disclosed aparticular method of making the compression disc-like supporting memberswherein the members are adapted to receive a loading in the direction ofthe rise axis of the foam, the foam exhibiting a markedly greaterresistance to compression strength in the direction of the rise axis ascontrasted to the strength in a direction transverse to the rise axis.

The objective of the present invention has been to provide an elongatedsubstantially foam structural element, in the nature of a two by four,which is able to withstand substantial compression loads but which ismuch lighter than wood and which has an insulative quality which ismarkedly superior to that of wood.

More specifically, it has been an objective of the invention to provideelongated bars of foamed plastic material sandwiched between cardboardstrips in which the rise axis of the foam is perpendicular to theelongated strips and parallel to the plane of the strips. This featureof the invention permits the use of the sinuous spacers of the inventiondisclosed in the copending application of Donald M. Turnbull, Ser. No.371,450, filed June 1, 1964, while utilizing the increased strength ofmaterial in a direction parallel to the rise axis as disclosed in theHeffner application.

It has been still another objective of the invention to provide aninsulative sandwich panel employing the elongated elements of thepresent invention.

This and other objectives of the invention will become more readilyapparent from the following detailed description in which:

FIG. 1 is a perspective view partly broken away of a panel structureemploying the present invention,

FIG. 2 is a perspective view illustrating the method of making thespacer elements employed in the panel of FIG. 1, and

FIGS. 3 and 4 are diagrammatic views of alternative forms of theinvention.

The structural elements formed in accordance with the present inventionand a floor structure utilizing them is illustrated in FIG. 1. Eachstructure element, indicated at 10, is constituted by a pair ofchipboard side walls 11 which are, in the illustrated example,approximately three-sixteenths of an inch thick and four inches high.Between the chipboard side walls 11 is polyurethane foam 12 which hasbeen foamed-in-place so that its rise axis is parallel to the side walls11 and perpendicular to the length of the element 10.

A principal use of the structural elements as indicated above, is in theformation of a floor structure for an insulated cargo body. Theformation of such a fioor structure is diagrammatically illustrated inFIG. 1. A more completely detailed statement of the manner in which thefloor structure is formed and related to the rest of the cargo bodystructure is set forth in the co-pending application of Heffner referredto above.

The elements 10 are employed as spacers in a sandwich panel 14 and aredisposed in spaced parallel relation between an upper sheet 15 and alower sheet 16. In the use of the panels as an insulated floor for acargo body, the spacers are on twelve inch centers so that, they willoverlie transverse members 17 which form a part of the main frame of thecargo body. By disposing the spacers under the cross members,compression forces which are imparted to the spacers will be transmitteddirectly to the cross members.

The panels are formed by first tacking or otherwise securing the spacersto one of the sheets and securing the other sheet on top of the spacers.The partially formed panel is supported on one edge with the spacersextending vertically and foamable polyurethane is introduced into thesections formed between adjacent spacers.

In the preferred form of the invention, at one edge of the panel a halfsize spacer 18 is fixed to the edge of the bottom sheet 16 and at theopposite longitudinal edge of the panel a half size spacer 18 is fixedto the edge of the upper sheet 15. Prior to the introduction of the foaminto the sandwich for-ms will be placed along the longitudinal edges ofthe panels to form rabbet grooves 20. Alternatively, the panels could beformed with planar longitudinal edges and the rabbet grooves sawed intothe edges, if rabbet grooves are desired.

The rabbet grooves are provided so as to permit adjacent panels to bejoined together in an overlapping relation providing a rabbet joint, asindicated at 21 in FIG. 1. The rabbet joint disposes two half sizespacers 18 on top of each other and overlying a cross member 17 of thevehicle frame so as to provide, at the rabbet joint, a strong jointwhich will resist compression stress and which will preserve the desiredinsulative integrity of the floor structure.

The formation of the structural elements is illustrated in FIG. 2. Twosinuous sheets 24 having their undulations extending in a horizontaldirection are mounted in spaced apart relation between two supports 25and 26. The support 25 is C-shaped and provides end wings 27 whichconfines the expanded foam at the ends of the sheets 24. The supports 25and 26 have sinuous surfaces conforming to the configuration of thesheets 24. After the sheets are supported in spaced apart relation asillustrated in FIG. 2, liquid foamable polyurethane is introduced insuflicient qualities to expand from the bottom of the cavity in thesheets 24 to the top of the cavity. In practice, this requires a volumeof liquid which is about onethirtieth of the space to be filled by it.The polyurethane expands and forms the foam structure which has a riseaxis in the direction of the arrow in FIG. 2. After the foam sets, thecomposite structure is sliced along the lines 28 thereby forming thestructural elements 10.

The foaming in place of the polyurethane to form the spacers 10 providesa structure which has a greater resistance to compression applied in thedirection of the rise axis. The strength is derived from two features.First, the foam and chipboard combine to form a composite structurehaving a resistance to compression far greater than the foam orchipboard taken alone would provide. Second, the expansion of the foamcauses the resulting cell structure to be elongated in the direction ofthe rise axis and the elongated cells provide a structure which has asubstantially greater resistance to the compression in the direction ofelongation than in a direction transverse to the elongation. Further,when the spacers are combined in the panel structure with thepolyurethane foamed-in-place about them, the chipboard is supported byfoam on both sides and is able to support tremendous compression loads.

It should be understood that the specific structure of the spacers issubject to modification without departing from the scope of theinvention, for example, a spacer may be formed as shown in FIG. 3 inwhich the side walls have been shifted 180 longitudinally with respectto each other so that the thickness of the spacers is non-uniform.

Still another embodiment is shown in FIG. 4, in which a single sinuouschipboard member 31 is used, that member being sandwiched between wallmembers 32 and 33. Foam is introduced and expanded in the cavities 34formed between the central corrugated member 31 and the wall members 32and 33. The technique of forming either of the members illustrated inFIGURES 3 and 4 would be substantially identical with that described inconnection with FIG. 2.

The advantages derived from the panel formed in accordance with thepresent invention can be appreciated by reference to FIG. 1. Instead oftwo by four spacers extending longitudinally of the respective panels,the invention employs the spacers 10 which, except for the thinchipboard walls 11 are entirely polyurethane. Since the foam isconsiderably lighter in weight and has a greatly increased resistance tothermal conductivity as contrasted to wooden two by fours, the resultantstructure is both lighter and of an improved insulative quality. Even atthe rabbet joint 21, no appreciable sacrifice in the insulative qualityof the fioor or of the ability of the floor to with stand thecompression loading has been made in View of the overlappingconfiguration of the joint and the reinforcement of it by the halfspacers 10.

While a marked improvement has been made in the insulative and weightaspects of the floor construction, the floor structure is more thanstrong enough to meet the requirements of usage, particularly thecompression loading occurring as a fork lift truck is driven into andout of the cargo space.

I claim:

1. A panel for receiving vertical compressive loading comprising:

two spaced generally parallel planar sheets,

a plurality of upright elongated structural reinforcing spacers for saidsheets each having a pair of spaced, generally parallel, thin elongatedstrips and foamable plastic of low thermoconductivity foamed in placebetween said strips such that the direction of columnar cellular growthof the foamable plastic is generally parallel to the sides of the stripsupward to the direction of pouring, producing elongation of the cellularnetwork in upward generally parallel orientation to define the rise axisof the foamable plastic, and said plastic foamed-in-place being incomplementary reinforcing relation with and between said strips with therise axis of the foamable plastic generally perpendicular to the lengthof said strips and generally parallel to a plane passing through heightof said strips,

said spacers being disposed between said sheets, the depth of the stripsand the rise axis of the plastic in the spacers being generallyperpendicular to the sheets, and

plastic foamed-in-place between said sheets and said spacers whereby theupright spacers are adapted to withstand vertical compressive loading inthe direction of the rise axis.

2. The invention according to claim 1, and said strips each beingundulated generally in the plane passing through the length of eachstrip and generally perpendicular to the rise axis of the foam plastic.

3. A panel construction suitable for mounting on a plurality oflongitudinally spaced transverse frame members comprising:

a panel for receiving vertical compressive loading comg, two spacedgenerally parallel planar sheets,

a plurality of upright elongated structural reinforcing spacers for saidsheets each spacer having a pair of spaced, generally parallel, thinelongated strips and foamable plastic of low thermoconductivity foamedin place between said strips such that the direction of columnarcellular growth of the foamable plastic is generally parallel to thesides of the strips upward to the direction of pouring, producingelongation of the cellular network in upward generally parallelorientation to define the rise axis of the foamable plastic, and saidplastic foamed-in-place being in complementary reinforcing relation withand between said strips with the rise axis of the foamable plasticgenerally perpendicular to the length of said strips and generallyparallel to a plane passing through height of said strips,

said spacers being disposed between said sheets, the depth of the stripsand the rise axis of the plastic in the spacers being generallyperpendicular to the sheets,

and plastic foamed-in-place between said sheets and said spacers wherebythe upright spacers are adapted to withstand vertical compressiveloading in the direction of the rise axis, and

a respective spacer being adapted to be placed disposed over acomplementary transverse frame member.

4. The invention according to claim 3, and said strips each beingundnlated generally in the plane passing through the length of eachstrip and generally perpendicular to the rise axis of the foam plastic.

References Cited UNITED STATES PATENTS 5/1945 Boyer 161-145 XR 5/1967Weber 156-210 EARL M. BERGERT, Primary Examiner H. F. EPSTEIN, AssistantExaminer U.S. Cl. X.R.

